Extract RNA from fixed cells

Hi,I fixed some primary murine bone marrow cells with 1%PFA (10 min) and then I kept them at 4C in a solution containing 3%Newborn Calf serum, 0.02%NaAz in 1x dPBS.
I need to extract RNA from these cells for a qRT-PCR experiment.
One of my colleague has a DNA FFPE kit to extract DNA from fixed cells:I could use its Proteinase K solution.
Which buffer/ solution should I use to resuspend my fixed cells and then add Proteinase K???

I will incubate at 55C and then 80C to remove the crosslinks of the PFA. After this step I'll use the E.Z.N.A. total RNA kit from Omega to extract RNA